1. The Field of the Invention
This invention relates to both electrosurgery and pressure sore pads. More particularly, this invention relates to pressure sore pads that conform to a patient""s body to minimize the incidence of decubitus ulcers or pressure sores, while being capable of acting as an effective and safe electrosurgical energy return without the need for conducting or dielectric gels.
2. The Relevant Technology
It is well known in the medical field that patients may develop decubitus ulcers, also known as pressure sores during a prolonged period of immobility. Typically, pressure sores develop in elderly patients who are confined to their beds or otherwise have limited movement. The pressure sores arise in those areas of the patient""s body where a prolonged pressure is applied to the patient""s tissue, usually over an underlying bony prominence. The prolonged pressure causes ischemic damage and tissue necrosis due to the maintenance of blood pressure above the normal capillary blood pressure of 32 mmHg. Although pressure sores typically occur in those patients who remain in one position for an extended period of time, pressure sores may arise from application of an intense pressure applied over a short period of time, approximately two hours, to a localized area, such as during various surgical procedures.
Generally, to prevent pressure sores the position of the patient is frequently changed to provide relief to the patient""s tissue. Additionally, the patient may rest upon one of a variety of mattresses or pads, such as foam pads, sheepskin layers, air filled mattresses, water mattresses, and the like, that reduce the pressure applied to the sensitive areas of the patient""s body, such as tissue over an underlying bony prominence. Although it is desirable to reposition the patient every 2 hours, whether or not the patient is lying on a pressure reducing mattress or pad, this is often difficult to perform during various surgical procedures, such as during electrosurgical procedures.
During an electrosurgical procedure, radio frequency (RF) power is employed to cut tissue and coagulate bleeding encountered in performing surgical procedures. For historical perspective and details of such techniques, reference is made to U.S. Pat. No. 4,936,842, issued to D""Amelio et al., and entitled xe2x80x9cElectrosurgical Probe Apparatus,xe2x80x9d the disclosure of which is incorporated by this reference.
As is known to those skilled in the medical arts, electrosurgery is widely used and offers many advantages including the use of a single surgical tool for both cutting and coagulation. Every monopolar electrosurgical generator system, however, must have an active electrode that is applied by the surgeon to the patient at the surgical site to perform surgery and a return path from the patient back to the generator. The active electrode at the point of contact with the patient must be small in size to produce a high current density in order to produce a surgical effect of cutting or coagulating tissue. The return electrode, which carries the same current as the active electrode, must be large enough in effective surface area at the point of communication with the patient such that a low density current flows from the patient to the return electrode. If a relatively high current density is produced at the return electrode, the temperature of the patient""s skin and tissue will rise in this area and can result in an undesirable patient burn. According to the Emergency Care Research Institute, a well-known medical testing agency, the heating of body tissue to the threshold of necrosis occurs when the current density exceeds 100 milliamperes per square centimeter. Furthermore, the Association for the Advancement of Medical Instrumentation (xe2x80x9cAAMIxe2x80x9d) has published standards that require that the maximum patient surface tissue temperature adjacent an electrosurgical return electrode shall not rise more than six degrees (6xc2x0) Celsius under stated test conditions.
Over the past twenty years, industry has developed products in response to the medical need for a safer return electrode in two major ways. First, they went from a small, about 12xc3x977 inches, flat stainless steel plate coated with a conductive gel placed under the patient""s buttocks, thigh, shoulders, or any location where gravity can ensure adequate contact area to a flexible electrode. These flexible electrodes, which are generally about the same size as the stainless steel plates, are coated with a conductive or dielectric polymer and have an adhesive border on them so they will remain attached to the patient without the aid of gravity. Upon completion of the electrosurgical procedure, these flat flexible electrodes are disposed of. By the early 1980""s, most hospitals in the United States had switched over to using this type of return electrode. These return electrodes are an improvement over the old steel plates and resulted in fewer patient return electrode burns but have resulted in additional surgical costs in the United States of several tens of millions of dollars each year. Even with this improvement, hospitals were still experiencing some patient burns caused by electrodes that would accidentally fall off or partially separate from the patient during surgery.
Subsequently, there was proposed a further improvement, an Electrode Contact Quality Monitoring System that would monitor the contact area of the electrode that is in contact with the patient and turn off the electrosurgical generator whenever there was insufficient contact area. Such circuits are shown, for example, in U.S. Pat. No. 4,231,372, issued to Newton, and entitled xe2x80x9cSafety Monitoring Circuit for Electrosurgical Unit,xe2x80x9d the disclosure of which is incorporated by this reference. This system has resulted in additional reduction in patient return electrode burns, but requires a special disposable electrode and an added circuit in the generator that drives the cost per procedure even higher. Fifteen years after this system was first introduced, fewer than 40 percent of all the surgical operations performed in the United States use this system because of its high costs.
Although various advances have been made in the electrosurgical arts, as discussed previously, there remains problems associated with preventing the creation of pressure sores during electrosurgical and other surgical procedures.
As briefly mentioned above, typically, a patient is placed upon a pressure reducing mattress or pad during a surgical procedure to reduce or substantially eliminate the forces applied to the sensitive areas of the body where tissue covers underlying bony prominences. One device that may be used to prevent pressure sores in an operational scenario is a foam pad, approximately 3-4 inches in height, which is placed between the operating table and the patient. Although foam pads have many advantages, such as being inexpensive and lightweight, they provide minimal relief to the patient while trapping body heat that may aid in generating pressure sores. Furthermore, by trapping heat the foam pad may aid in increasing the patient""s tissue temperature so that during an electrosurgical procedure the tissue temperatures may rise above the six degrees (6xc2x0) Celsius temperature rise required by the AAMI. Additionally, foam pads are typically discarded proceeding a surgical procedure since they are difficult to sterilize and clean. Furthermore, the material forming the foam pad may release lethal fumes if ignited during a fire.
An alternate pressure reducing mattress or pad is a layer of sheepskin placed on the operating table. Unfortunately, sheepskin provides poor protection to the patient and does not effectively distribute the patient""s pressure throughout the entire surface upon which they are laying. As with the foam pad discussed above, sheepskin is difficult to sterilize and clean following a surgical procedure.
Yet another type of pressure reducing device is the air inflated mattress that includes a vinyl sleeve filled with air to a desired pressure. Unfortunately, the air mattress must be significantly pressurized to prevent the patient from touching the bottom surface upon which the mattress is placed. In the event the patient touches the bottom surface, there is a chance for development of a pressure sore. Additionally, in order to maintain the required pressure, typically, a pump is connected to the mattress to monitor the pressure of air contained within the mattress and pump additional air into the mattress as required. With a patient placed upon the movable air mattress, which is in turn resting upon an operating table, the patient is lying upon two flexible surfaces. The patent is thereby placed in an unstable and precarious position during surgical procedures. Additionally, air-type mattresses are expensive to maintain due to the need for a pump to maintain the required air pressure. Furthermore, the air mattress may easily be perforated, thereby leaking air and reducing the effectiveness of the mattress to maintain the patient distal from the surface upon which the mattress is placed.
A similar pressure-reducing device to the air filled mattress is the water type mattress. The water-type mattress has a similar form to that of the air mattress; however, water is pumped through the mattress rather than air. Unfortunately, the water type mattress suffers from many of the limitations of the air type mattress. Additionally, in the event that the water mattress leaks, a large amount of water would be discharged onto the floor surrounding the patient, thereby making it dangerous for individuals to walk and work in close proximity to the patient.
Although many of the above-described limitations are alleviated in general use within a hospital, each recited pressure sore device has various drawbacks with respect to their use during electrosurgical procedures. For example, in the event a foam type mattress is used during an electrosurgical procedure, there is a chance that the foam pad may ignite, thereby burning the patient and also emitting lethal fumes within the operating theater.
With respect to the air and water type mattresses, inclusion of the required pumps to maintain the desired pressure for a long period of time increases the amount of equipment necessary stored within an operating theater. As such, with more equipment within a limited space the ability of the surgeon to move around reduces. In the event of a water leak from the water mattress, there is the possibility that of electrocution of the patient and/or the physicians and nurses in the operating theater as well as the possibility of shorting of the electrosurgical return electrode.
Therefore, it would be an advance in the present electrosurgical art to provide an electrosurgical electrode that is self-limiting, while reducing the pressure sore creation.
The present invention overcomes the problems of the prior art by providing a return electrode that eliminates patient bums without the need for expensive disposable electrodes and monitoring circuits in specialized RF generators, while also providing a pressure sore pad that minimizes the occurrence of pressure sores for patients having electrosurgical procedures.
Briefly, the improved return electrode according to the preferred embodiment of the invention hereof includes an effective surface area that is larger than other return electrodes that have been disclosed or used in surgery previously. It is so large and so adapted for positioning relative to the body of a patient that it eliminates the need for conductive or dielectric gels. Moreover, the exposed surface is of a material that is readily washable, disenfectable, and/or sterilizable so as to facilitate easy and rapid conditioning for repeated reuse. It employs geometries and materials whose impedance characteristics, at typically used electrosurgical frequencies, are such that it self-limits current densities (and corresponding temperature rises) to safe thresholds, should the effective area of the working surface of the electrode be reduced below otherwise desirable levels. Accordingly, the need for the foregoing expensive monitoring circuits in specialized RF generators is eliminated. Furthermore, the improved return electrode incorporates a pressure sore pad that prevents the formation of pressure sores, while aiding with current transfer between the patient and the return electrode.
In accordance with a feature of the invention, an electrosurgical return electrode is made sufficiently large to present sufficiently low electrical impedance and low current densities at typical electrosurgery frequencies used in medical procedures to reduce the possibility of excessive temperature elevation in adjacent patient tissue, (i.e., by maintaining temperature (xe2x80x9cTxe2x80x9d) rise below six degrees (6xc2x0) Celsius) thereby avoiding tissue necrosis or other undesired patient trauma.
In accordance with yet another feature of the invention, the working surface of the electrode (the electrode surface that is in contact with or in close proximity to the patient) is made sufficiently large in area so that in normal use, current flow will not be reduced to a point where it impedes the surgeon""s ability to perform surgery at the surgical site.
In accordance with yet another feature of the invention, in one embodiment, the electrosurgical return electrode has a multi-layer construction, including an electrode and a pressure sore pad.
In accordance with yet another feature of the invention, in one embodiment, controlled electrical conductivity is imparted to the electrode by the inclusion therein of electrically conductive materials such as conductive threads or carbon black, thus conditioning conductivity as a function of surface area to levels which limit passage of current therethrough to safe values.
In accordance with yet another feature of the invention, in one embodiment, the electrosurgical return electrode includes a pressure sore pad with an integrally formed electrode coupled to the body of the pressure sore pad. As such, the material forming the pressure sore pad acts as, alternatively, a conductive layer or an insulative layer.
In accordance with yet another feature of the invention, the electrosurgical return electrode includes an interior material that is conductive while providing pressure relief to the patient.
In accordance with still another feature of the invention, the electrosurgical return electrode includes heating and cooling capabilities to either heat or cool a patient during a surgical procedure.
In accordance with another feature of the invention, the electrosurgical return electrode includes a pressure sore pad that provides heating and cooling capabilities to either heat or cool a patient during a surgical procedure, while the pad is self limiting and aids with the reduction in the creation of decubitus ulcers or pressure sores.
In accordance with yet another feature of the invention, in another embodiment, a moisture impervious working surface is provided for positioning adjacent an adjoining surface of the body of a patient, thus facilitating cleansing and reuse of the electrosurgical electrode.
In accordance with yet another feature of the invention, the aforementioned moisture impervious working surface is made resistant to normally encountered cleaning, disinfecting, and sterilizing agents, thus further facilitating cleansing and reuse.
In accordance with yet another feature of the invention, in another embodiment, a sleeve is provided for cooperative use with the electrosurgical electrode, thus protecting the electrode and the pressure sore pad from inadvertent damage that might occur, for example, from accidental contact of the active electrosurgical instrument with the electrode surface.
In accordance with yet another feature of the invention, the electrical impedance of the materials in and adjacent to the working surface of the electrode is sufficiently elevated so as to limit current density at the working surface to a level below the threshold of patient tissue trauma, thus providing a self-limiting characteristic to prevent patient trauma in the event of accidental reduction of the effective working surface of the electrode.
In accordance with yet another feature of the invention, in one embodiment, the electrosurgical electrode is form-fitted to the operating table on which the electrosurgical procedure is to be performed, thus facilitating realization of other features of the invention.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.